A great many thing are wrong with Ridley Scott’s “Robin Hood” — it’s too long, too drab, and too tedious, to name a few — but let’s start with its title. Just as Tim Burton’s “Alice in Wonderland” sounded like a remake but was actually a sequel, Scott’s “Robin Hood” is not a retelling of the jolly adventure story but a prequel to it. It’s “The Origins of Robin Hood.” The film is 140 minutes long, and it ends at the part where things are just starting to get interesting. The story that comes after this one — that sounds fun!

But not this one. Ugh, what a load this is. It came from a screenplay by Ethan Reiff and Cyrus Voris that retold the familiar story from the sheriff of Nottingham’s point of view. Naturally, once the screenplay was purchased, the Hollywood wizards completely changed everything about it that was original or unique and hired the prolific rewriter Brian Helgeland (“L.A. Confidential,” “Mystic River”) to turn it into “Gladiator.” Tellingly, the sheriff — originally the main character — is barely in the film.

Heck, even Robin Hood is barely in the film. Played by Russell Crowe, he’s Robin Longstride most of the time, and impersonating someone else the rest of the time. (This version of “Robin Hood” is like a version of “Batman” that ends with Bruce Wayne deciding to become Batman.) Having fought alongside King Richard (Danny Huston) in the Crusades for 10 years, he’s now on his way back to England, in A.D. 1199, when a fellow soldier named Robert Loxley (Douglas Hodge) is killed in a French ambush. Loxley’s dying wish is that Robin return his (Loxley’s) sword to his father back home in Nottingham.

Well, guess who Loxley’s wife (now widow) is? None other than Marian (Cate Blanchett), who is not a Maid but a Lady. And guess who Loxley’s father is? A blind old man — played by Max von Sydow, who played a soldier returning from the Crusades in Ingmar Bergman’s “The Seventh Seal” — who happens to have known Robin’s father before he (Robin’s father) abandoned him years ago.

For reasons too embarrassing and contrived to relate here, Robin Longstride is compelled to pretend to be Loxley’s son and Marian’s husband, to fool the sheriff (Matthew Macfadyen). Yes, this version of “Robin Hood” is like a romantic comedy where two people who don’t get along at first are forced to work together.

Meanwhile, Richard’s brother, Prince John (Oscar Isaac), is whoring it up with a French tart and embarrassing the Queen Mother (Eileen Atkins). In charge of the kingdom while Richard is off killing Muslims, John raises taxes, which is necessary because his brother’s Muslim-killing war is expensive. In Nottingham, there’s a new friar named Tuck (Mark Addy) who plays no significant role whatsoever but is here because the movie is called “Robin Hood” and there damn well better be a Friar Tuck in it.

And what of Robin’s merry men? Well, there are three of them — Little John (Kevin Durand), Will Scarlet (Scott Grimes), and Allan A’Dayle (Alan Doyle) — and they are generally convivial, if not merry, per se. But they’re the only ones. Oh, and Prince John, I guess. He’s pretty upbeat. He isn’t evil or greedy, though, like you were expecting. Just sort of weaselly and in-over-his-head, and keen to ignore the wise counsel of royal adviser William Marshal (William Hurt).

So if the sheriff is neutered and Prince John is merely inept, who are the bad guys? The French, duh. English-born turncoat Godfrey (Mark Strong) pretends to work with Prince John but secretly advises France’s King Philip (Jonathan Zaccai), who’s planning an invasion.

Such a crowded, busy movie! And so somber, except when it takes a moment, here and there, to pander to the lowest common denominator with a broad joke or two. Ridley Scott shoots the action scenes the way he always shoots action scenes — competently, energetically — but without any life. His frequent collaborator, Mr. Crowe, is likewise lifeless, as he often is in action roles. (Put him in something more character-based, like “The Insider,” or even last year’s “State of Play,” and you can’t take your eyes off him.) Cate Blanchett is luminous in a thankless role. And what’s up with the absurd finale, where suddenly everyone is a warrior? And what the eff does any of this have to do with Robin Hood?

This is a film with no distinguishing characteristics. If it mugged you in an alley, you would only be able to tell the police, “Well, it was two hours and 20 minutes long, and it had Russell Crowe, and there were a lot of bows and arrows, and I think the Prince John character was kind of fun, sometimes.” The police artist would do a composite sketch, and they’d show it on the news, and everyone would say, “Wow, that looks a lot like ‘Gladiator.’ Are you sure it wasn’t ‘Gladiator’ that mugged you? Has anyone seen ‘Gladiator’ lately?” And you’d say no, this was similar to “Gladiator,” only more average, less fun, and slightly shorter.